The following background information is provided to assist the reader in understanding the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
The present invention will be discussed in an application involving a movable door for a passenger transit vehicle, as those skilled in the art will readily understand its use in other applications.
Lock mechanisms for selectively locking and unlocking a single door or a pair of doors in a transit vehicle are well known in the art. Reliability of such lock mechanisms have implications on overall operation and safety of the passenger vehicle as well as ability for passengers to ingress and egress such passenger vehicle.
The lock mechanism must positively and reliably engage the door to prevent unwanted opening thereof during vehicle motion so not to endanger the passengers. The lock mechanism must also reliably disengage from such door enabling a controlled opening thereof at the station for passenger ingress and egress. Failure of the lock mechanism to reliably disengage from the door will result in passenger inconvenience and operational schedule delays. Additionally, the lock mechanism must be provided with capabilities enabling a passenger to manually unlock and open the door, especially during an emergency situation.
Reliability of the lock mechanism operation is generally associated with the quantity of individual components with a smaller number of components being advantageous for a more reliable operation. Such smaller number of components is also desirable to simplify assembly, installation and adjustment of such lock mechanism as well as to reduce its manufacturing cost. The reliability of operation is further generally associated with the working arrangement between individual components.
U.S. Pat. No. 6,139,073 teaches one type of such lock mechanism for selectively locking and unlocking a single sliding door of the passenger vehicle. The lock mechanism has a base member for attachment to the passenger vehicle and a lock cam having a slot formed therein for engaging a lock mechanism element attached to the door. A pivot is connected to the base member and to the lock cam to provide a rotary connection of the lock cam to such base member.
A power lock actuator is attached to the base member and includes a linearly moveable actuator portion for engaging the lock cam for preventing unwanted rotation of the lock cam to lock the door. Such movable actuator portion is guided by a plurality of rollers to maintain alignment during operation. The actuator also has an energized actuator portion for withdrawing the moveable actuator portion from engagement with the lock cam to release the lock cam and unlock the door. The energized actuator portion is connected to a control system of the transit vehicle door.
The lock mechanism further includes a manual release operable by a person. The manual release is mounted to engage the moveable actuator portion to move it from engagement with the lock cam enabling release thereof and hence enabling manual unlocking and subsequent opening of the sliding door.
The lock mechanism additionally includes a sprag member engageable with the manual release and a biasing means connected to the sprag for biasing the sprag into engagement with the lock cam after the manual release has been used to prevent unwanted locking of such sliding door requiring reset of the sprag before the sliding door can be locked. A plurality of limit switches is associated with the movable actuator portion and the sprag for providing status signals to the control system of the passenger vehicle during lock mechanism operation.
It has been found that, for providing guidance of the movable actuator portion during locking and unlocking phases, such movable actuator portion must be machined to a very close tolerance and such plurality of guiding rollers must be adjusted to yet another set of very close tolerances during lock mechanism assembly to prevent unwanted friction and binding between actuator portion and lock cam during operation.
It has also been found that incorporation of such plurality of rollers, additional machining and adjustment requirements excessively increased lock mechanism cost. Additionally, it has been found that the sprag biasing means are subjected to high stresses due to spatial limitations within passenger vehicle structure and resulting configuration of the base member.
It is, therefore, desirable to provide an improved lock mechanism arrangement overcoming the aforementioned disadvantages and meeting the original spatial envelope constraints.
The lock mechanism taught by U.S. Pat. No. 6,139,073 is suitable only for locking the single sliding door of the passenger vehicle driven by a dedicated door drive mechanism even when such passenger vehicle has a pair of doors disposed in a door portal aperture for passenger ingress and egress. Such application is generally known as an independent door operation mode. Since a wide variety of passenger vehicles utilize a single door drive mechanism for driving the pair of doors, in what is generally known as a bi-parting door operation mode, it is desirable to utilize a single lock mechanism for locking such pair of bi-parting doors to reduce overall implementation costs.